THE EFFECTS OF CONCENTRATION ON PARTITIONING OF FLEXIBLE CHAINS INTO PORES

Equilibrium partitioning between bulk solution and pores was investigated by computer experiment using the Monte Carlo technique. In a multichain athermal system, self-avoiding walks of up to 60 steps were generated on a simple cubic lattice with variable pore size and chain concentration. The results demonstrate that the constraints imposed by the pores and/or neighbouring chains reduce the chain entropy. The entropy related parameter, the partition coefficient K (the equilibrium pore-to-bulk concentration ratio) increases linearly with bulk concentration ø. A maximum concentration dependence of K was found for large pores characterized by a coil-to-pore dimension ratio λ of about 0.1-0.3. In this range the increase in bulk concentration brings about a dramatic enhancement of partitioning into pores. The results of computer experiments are compared with predictions of hard-sphere solutes theory and with static and gel-chromatographic measurements of the partitioning equilibrium. The implications of the concentration-dependent coefficient K for hindered transport of flexible polymers inside pores are briefly discussed. © 1990.